WO2012137375A1

WO2012137375A1 - Nonaqueous secondary battery separator and nonaqueous secondary battery

Info

Publication number: WO2012137375A1
Application number: PCT/JP2011/074258
Authority: WO
Inventors: 西川　聡
Original assignee: 帝人株式会社
Priority date: 2011-04-08
Filing date: 2011-10-21
Publication date: 2012-10-11
Also published as: CN103155219B; TW201242136A; TWI497790B; JPWO2012137375A1; CN103155219A; EP2696391B1; KR20130036043A; KR101297769B1; US20130089770A1; EP2696391A4; JP5432417B2; US9065119B2; EP2696391A1

Abstract

The purpose of the present invention is to provide a nonaqueous secondary battery separator having excellent adhesion to an electrode, capable of ensuring sufficient ion permeability after adhesion to the electrode, and provided with an adhesive porous layer having a uniform porous structure and sufficient mechanical properties to withstand hot pressing. This nonaqueous secondary battery separator is: provided with a porous substrate and an adhesive porous layer that contains a polyvinylidene fluoride resin and is formed on at least one surface of the porous substrate; and characterized in that the porosity of the adhesive porous layer is 30-60%, and the average pore diameter thereof is 1-100nm.

Description

Nonaqueous secondary battery separator and nonaqueous secondary battery

The present invention relates to a separator for a non-aqueous secondary battery and a non-aqueous secondary battery.

Non-aqueous secondary batteries such as lithium ion secondary batteries are widely used as power sources for portable electronic devices such as notebook computers, mobile phones, digital cameras, and camcorders. Further, in recent years, these batteries have been studied for application to automobiles and the like because of their high energy density.

With the reduction in size and weight of portable electronic devices, the exterior of non-aqueous secondary batteries has been simplified. Initially, stainless steel battery cans were used as the exterior, but aluminum can exteriors have been developed, and now soft pack exteriors made of aluminum laminate packs have also been developed. In the case of an aluminum laminate-made soft pack exterior, since the exterior is soft, a gap may be formed between the electrode and the separator along with charge and discharge, and there is a technical problem that the cycle life is deteriorated. From the viewpoint of solving this problem, a technique for bonding an electrode and a separator is important, and many technical proposals have been made.

As one of the proposals, a technique is known that uses a separator in which a porous layer made of a polyvinylidene fluoride resin (hereinafter also referred to as an adhesive porous layer) is formed on a polyolefin microporous film, which is a conventional separator ( For example, see Patent Document 1). When the adhesive porous layer is hot-pressed over the electrode in a state containing the electrolytic solution, the electrode and the separator can be satisfactorily bonded and can function as an adhesive. Therefore, the cycle life of the soft pack battery can be improved.

Further, when a battery is manufactured using a conventional metal can exterior, a battery element is manufactured by winding the electrode and the separator in an overlapped state, and the element is enclosed in the metal can exterior together with an electrolytic solution. Is made. On the other hand, when producing a soft pack battery using the separator as in Patent Document 1 described above, a battery element is produced in the same manner as the battery with the above metal can, and this is put together with the electrolyte in the soft pack exterior. A battery is produced by encapsulating and finally adding a hot press process. Therefore, in the case of using the separator having the adhesive porous layer as described above, a battery element can be produced in the same manner as the battery with the above metal can outer case. There is also an advantage that no change is required.

From the background described above, various technical proposals have been made in the past for separators in which an adhesive porous layer is laminated on a polyolefin microporous membrane. For example, in Patent Document 1, a new technical proposal has been made focusing on the porous structure and thickness of a polyvinylidene fluoride resin layer from the viewpoint of ensuring sufficient adhesion and ion permeability.

Japanese Patent No. 4127989

Incidentally, a positive electrode or a negative electrode of a general non-aqueous secondary battery includes a current collector, and an active material layer including an electrode active material and a binder resin formed on the current collector. And the adhesive porous layer mentioned above adhere | attaches with respect to the binder resin in an electrode, when making it join with an electrode by hot press. Therefore, in order to ensure better adhesiveness, it is preferable that the amount of the binder resin in the electrode is large.

However, in order to further increase the energy density of the battery, it is necessary to increase the content of the active material in the electrode, and it is preferable that the content of the binder resin is small. Therefore, in order to ensure sufficient adhesion in the prior art, it is necessary to perform hot pressing under severe conditions such as higher temperature and higher pressure. And in the prior art, when it hot-presses on such severe conditions, there existed a problem that the porous structure of the adhesive porous layer which consists of a polyvinylidene fluoride resin will be crushed. For this reason, the ion permeability after the hot pressing step is insufficient, and it is difficult to obtain good battery characteristics.

Conventionally, the binder resin used for the electrode is generally a polyvinylidene fluoride resin, but in recent years, the use of styrene-butadiene rubber is increasing. For an electrode using such a styrene-butadiene rubber, it has been difficult to obtain sufficient battery characteristics while achieving both ion permeability and adhesiveness in a separator having a conventional adhesive porous layer.

For example, in the separator described in Patent Document 1, the porosity of the porous layer made of polyvinylidene fluoride resin is 50 to 90%, which is a very high porosity. However, such an adhesive porous layer having a high porosity has a problem that when subjected to a hot press process under severe bonding conditions, the porous structure is crushed due to insufficient mechanical properties. . Furthermore, pores having a pore diameter of 0.05 to 10 μm are scattered on the surface of the adhesive porous layer. However, with such a non-uniform surface pore structure, when the amount of binder resin in the electrode is reduced and the hot press conditions are relaxed, both electrode adhesion, ion permeability and battery cycle characteristics are compatible. Is difficult.

Against this background, the present invention is superior in adhesion to the electrode compared to the prior art, can ensure sufficient ion permeability even after being bonded to the electrode, and can withstand a mechanical press sufficiently. It aims at providing the separator for non-aqueous secondary batteries provided with the adhesive porous layer which has a physical property and a uniform porous structure.

The present invention adopts the following configuration in order to solve the above problems.
1. A separator for a non-aqueous secondary battery comprising a porous substrate and an adhesive porous layer containing a polyvinylidene fluoride-based resin formed on at least one surface of the porous substrate, the adhesive The porous layer has a porosity of 30% to 60%, and an average pore size of 1 nm to 100 nm.
2. 2. The non-aqueous system according to 1 above, wherein the adhesive porous layer has a porosity of 30% to 50%, and the polyvinylidene fluoride resin contains 98 mol% or more of vinylidene fluoride. Secondary battery separator.
3. 1 or 2 above, wherein the weight of the adhesive porous layer formed on one surface of the porous substrate is 0.5 g / m ² or more and 1.5 g / m ² or less. The separator for non-aqueous secondary batteries as described.
4). 4. The separator for a non-aqueous secondary battery according to any one of 1 to 3 above, wherein the adhesive porous layer is formed on both front and back surfaces of the porous substrate.
5. The total weight of both surfaces of the adhesive porous layer formed on both surfaces of the porous substrate is 1.0 g / m ² or more and 3.0 g / m ² or less, and one surface side of the adhesive porous layer 5. The separator for a non-aqueous secondary battery as described in 4 above, wherein the difference between the weight of the other side and the weight on the other side is 20% or less with respect to the total weight of both sides.
6). 6. The separator for a non-aqueous secondary battery according to any one of 1 to 5 above, wherein the porous substrate is a polyolefin microporous membrane containing polyethylene.
7. 6. The separator for a non-aqueous secondary battery according to any one of 1 to 5 above, wherein the porous substrate is a polyolefin microporous film containing polyethylene and polypropylene.
8). The non-aqueous two-layer film according to 7 above, wherein the polyolefin microporous membrane has a structure of at least two layers, one of the two layers including polyethylene and the other layer including polypropylene. Secondary battery separator.
9. 9. A non-aqueous secondary battery using the separator according to any one of 1 to 8 above.

According to the present invention, the adhesion to the electrode is superior to that of the prior art, sufficient ion permeability can be secured even after bonding with the electrode, and further, the mechanical properties are uniform and uniform enough to withstand hot pressing. A separator for a nonaqueous secondary battery provided with an adhesive porous layer having a porous structure can be provided. By using such a separator of the present invention, it is possible to provide a non-aqueous secondary battery having a high energy density and a high performance aluminum laminate pack exterior.

A separator for a non-aqueous secondary battery according to the present invention includes a porous substrate and an adhesive porous layer containing a polyvinylidene fluoride-based resin formed on at least one surface of the porous substrate. A separator for an aqueous secondary battery, wherein the adhesive porous layer has a porosity of 30% to 60% and an average pore diameter of 1 nm to 100 nm. Hereinafter, the present invention will be described in detail. In the following, the numerical value range indicated by “˜” means a numerical range including an upper limit value and a lower limit value.

[Porous substrate]
In the present invention, the porous substrate means a substrate having pores or voids therein. Examples of such a substrate include a microporous film, a porous sheet made of a fibrous material such as a nonwoven fabric and a paper sheet, or one or more other porous layers laminated on the microporous film or the porous sheet. The composite porous sheet etc. which were made to be mentioned can be mentioned. A microporous membrane is a membrane that has a large number of micropores inside and a structure in which these micropores are connected, and allows gas or liquid to pass from one surface to the other. Means.

The material constituting the porous substrate can be either an organic material or an inorganic material having electrical insulation. In particular, from the viewpoint of imparting a shutdown function to the base material, it is preferable to use a thermoplastic resin as a constituent material of the base material. Here, the shutdown function is a function to prevent the thermal runaway of the battery by blocking the movement of ions by melting the thermoplastic resin and closing the pores of the porous substrate when the battery temperature rises. Say. As the thermoplastic resin, a thermoplastic resin having a melting point of less than 200 ° C. is suitable, and polyolefin is particularly preferable.

A polyolefin microporous membrane is suitable as a porous substrate using polyolefin. As the polyolefin microporous membrane, a polyolefin microporous membrane having sufficient mechanical properties and ion permeability and applied to a conventional separator for a non-aqueous secondary battery can be used. The polyolefin microporous membrane preferably contains polyethylene from the viewpoint of having the shutdown function described above, and the polyethylene content is preferably 95% by weight or more.

Separately, a polyolefin microporous film containing polyethylene and polypropylene is preferable from the viewpoint of imparting heat resistance that does not easily break when exposed to high temperatures. Examples of such a polyolefin microporous membrane include a microporous membrane in which polyethylene and polypropylene are mixed in one sheet. Such a microporous membrane preferably contains 95% by weight or more of polyethylene and 5% by weight or less of polypropylene from the viewpoint of achieving both a shutdown function and heat resistance. Further, from the viewpoint of achieving both a shutdown function and heat resistance, the polyolefin microporous membrane has a structure of at least two layers, and one of the two layers includes polyethylene and the other layer includes polypropylene. A polyolefin microporous membrane having a structure is also preferred.

The weight average molecular weight of polyolefin is preferably 100,000 to 5,000,000. If the weight average molecular weight is less than 100,000, it may be difficult to ensure sufficient mechanical properties. On the other hand, if it exceeds 5 million, the shutdown characteristics may be deteriorated or molding may be difficult.

Such a polyolefin microporous membrane can be produced, for example, by the following method. That is, (i) a step of extruding a molten polyolefin resin from a T-die to form a sheet, (ii) a step of subjecting the sheet to crystallization treatment, (iii) a step of stretching the sheet, and (iv) heat treatment of the sheet A method of forming the microporous film by sequentially performing the steps is performed. (I) a step of melting a polyolefin resin together with a plasticizer such as liquid paraffin, extruding it from a T-die and cooling it to form a sheet, (ii) a step of stretching the sheet, (iii) Examples include a method of forming a microporous film by sequentially performing a step of extracting a plasticizer from the sheet, and (iv) a step of heat-treating the sheet.

Examples of porous sheets made of fibrous materials include polyesters such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene, heat-resistant polymers such as aromatic polyamides and polyimides, polyethersulfone, polysulfone, polyetherketone, and polyetherimide. Or a porous sheet made of a mixture of these fibrous materials.

As the composite porous sheet, a structure in which a functional layer is laminated on a porous sheet made of a microporous film or a fibrous material can be adopted. Such a composite porous sheet is preferable in that a further function can be added by the functional layer. As the functional layer, for example, from the viewpoint of imparting heat resistance, a porous layer made of a heat resistant resin or a porous layer made of a heat resistant resin and an inorganic filler can be used. Examples of the heat resistant resin include one or more heat resistant polymers selected from aromatic polyamide, polyimide, polyethersulfone, polysulfone, polyetherketone, and polyetherimide. As the inorganic filler, a metal oxide such as alumina or a metal hydroxide such as magnesium hydroxide can be suitably used. Examples of the composite method include a method of coating a functional sheet on a porous sheet, a method of bonding with an adhesive, and a method of thermocompression bonding.

In the present invention, the film thickness of the porous substrate is preferably in the range of 5 to 25 μm from the viewpoint of obtaining good mechanical properties and internal resistance. The Gurley value (JIS P8117) of the porous substrate is preferably in the range of 50 to 800 seconds / 100 cc from the viewpoint of preventing short circuit of the battery and obtaining sufficient ion permeability. The puncture strength of the porous substrate is preferably 300 g or more from the viewpoint of improving the production yield.

[Polyvinylidene fluoride resin]
A polyvinylidene fluoride resin is applied to the separator for a non-aqueous secondary battery of the present invention. As the polyvinylidene fluoride-based resin, a homopolymer of vinylidene fluoride (that is, polyvinylidene fluoride), a copolymer of vinylidene fluoride and another copolymerizable monomer, or a mixture thereof can be used. As the monomer copolymerizable with vinylidene fluoride, for example, one kind or two or more kinds such as tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, trichloroethylene, or vinyl fluoride can be used. Such a polyvinylidene fluoride resin can be obtained by emulsion polymerization or suspension polymerization.

The polyvinylidene fluoride resin used for the separator for a non-aqueous secondary battery of the present invention preferably contains 98 mol% or more of vinylidene fluoride as a structural unit. When 98 mol% or more of vinylidene fluoride is contained, sufficient mechanical properties and heat resistance can be secured even under severe hot press conditions.

The polyvinylidene fluoride resin used in the present invention preferably has a weight average molecular weight in the range of 300,000 to 3,000,000. The range of 300,000 to 2,000,000 is more preferable, and the range of 500,000 to 1,500,000 is more preferable. If the weight average molecular weight is less than 300,000, the adhesive porous layer may not have sufficient mechanical properties to withstand the adhesion process with the electrode, and sufficient adhesion may not be obtained. Further, when the weight average molecular weight is larger than 3 million, the viscosity of the slurry containing the resin is increased, so that it is difficult to form the adhesive porous layer, or good crystals are formed in the adhesive porous layer. This is not preferable because it may be difficult to obtain a suitable porous structure.

[Adhesive porous layer]
In the present invention, the porous structure of the adhesive porous layer is an important technical element. The porous structure has a porosity of 30 to 60% and an average pore diameter of 1 to 100 nm. Here, the adhesive porous layer is composed of a polyvinylidene fluoride-based resin, has a number of micropores inside, and has a structure in which these micropores are connected. It means a porous layer in which gas or liquid can pass from one side to the other side. Further, the average pore diameter is calculated by using the pore surface area S of the adhesive porous layer calculated from the nitrogen gas adsorption amount and the pore volume V of the adhesive porous layer calculated from the porosity. Is calculated from the following formula 1, assuming that is cylindrical.

d = 4 × V / S (Formula 1)
d: average pore diameter of the adhesive porous layer V: pore volume of the adhesive porous layer S: pore surface area of the adhesive porous layer

In order to obtain the pore surface area S of the adhesive porous layer, first, the specific surface area (m ² / g) of the porous substrate applied by the nitrogen gas adsorption method and the composite film formed with the adhesive porous layer The specific surface area (m ² / g) is measured. Then, the specific surface area is multiplied by the basis weight (g / m ² ) to obtain the pore surface area per unit area of the sheet, and the pore surface area of the porous substrate is subtracted from the pore surface area of the composite membrane. Thus, the pore surface area S of the adhesive porous layer is calculated.

In the present invention, the porosity of the adhesive porous layer is 30 to 60%. When the porosity of the adhesive porous layer is 30% or more, good ion permeability can be obtained, and sufficient battery characteristics can be obtained. If the porosity of the adhesive porous layer is 60% or less, sufficient mechanical properties can be obtained to such an extent that the porous structure is not crushed when adhered to the electrode in the hot press step. In addition, when the porosity is 60% or less, the surface porosity becomes low and the area occupied by the polyvinylidene fluoride resin having an adhesive function increases, so that sufficient adhesive force can be secured. The porosity of the adhesive porous layer is more preferably 30 to 50%.

In the present invention, the average pore size of the adhesive porous layer is 1 to 100 nm. If the average pore size of the adhesive porous layer is 100 nm or less, it becomes easy to have a porous structure in which uniform pores are uniformly dispersed, and the adhesion points with the electrode are uniformly dispersed, so that good adhesion can be obtained. Can do. In that case, since the movement of ions becomes uniform, sufficient cycle characteristics can be obtained, and even better load characteristics can be obtained. On the other hand, the average pore diameter is preferably as small as possible from the viewpoint of uniformity, but it is practically difficult to form a porous structure smaller than 1 nm. Further, when the adhesive porous layer is impregnated with the electrolytic solution, the polyvinylidene fluoride-based resin swells. However, if the average pore diameter is too small, the pores are blocked by swelling and the ion permeability is inhibited. Also from such a viewpoint, the average pore diameter is preferably 1 nm or more. The average pore size of the adhesive porous layer is more preferably 20 to 100 nm.

The above-described swelling due to the electrolytic solution varies depending on the type of polyvinylidene fluoride resin and the composition of the electrolytic solution, and the degree of failure associated with the swelling also varies. When paying attention to the polyvinylidene fluoride resin, for example, when a copolymer containing a large amount of a copolymer component such as hexafluoropropylene is used, the polyvinylidene fluoride resin tends to swell. Therefore, in the present invention, it is preferable to select a polyvinylidene fluoride-based resin that does not cause the above-mentioned problems associated with swelling in the range of an average pore diameter of 1 to 100 nm. From such a viewpoint, it is preferable to use a polyvinylidene fluoride resin containing 98 mol% or more of vinylidene fluoride.

When attention is paid to the electrolytic solution, for example, when an electrolytic solution having a high cyclic carbonate content such as ethylene carbonate or propylene carbonate having a high dielectric constant is used, the polyvinylidene fluoride resin easily swells. As a result, problems associated with the above-mentioned swelling are likely to occur. In this regard, if a polyvinylidene fluoride-based resin containing 98 mol% or more of vinylidene fluoride is used, sufficient ion permeability can be obtained even when an electrolytic solution consisting only of a cyclic carbonate is applied, and good battery performance is obtained. Since it is obtained, it is preferable.

The adhesive porous layer according to the present invention is characterized in that its average pore diameter is very small as compared with the conventional one, although it has an appropriate porosity as a separator for non-aqueous secondary batteries. Is. This means that a fine porous structure is developed and uniform. According to such a porous structure, since the movement of ions at the interface between the separator and the electrode becomes more uniform as described above, a uniform electrode reaction can be obtained. Therefore, the effect of improving the load characteristics and cycle characteristics of the battery can be obtained. In addition, since the polyvinylidene fluoride resin is uniformly distributed on the separator surface, the adhesion with the electrode becomes better.

Furthermore, the porous structure of the present invention also improves ion migration at the interface between the porous substrate and the adhesive porous layer. In general, the laminated separator is likely to be clogged at the interface between the two layers, and the ion migration is likely to be lowered. Therefore, it may be difficult to obtain good battery characteristics. However, the adhesive porous layer in the present invention has a fine porous structure, is uniform, and has a relatively large number of pores. Therefore, since the probability that the hole of the porous substrate and the hole of the adhesive porous layer can be satisfactorily connected increases, clogging at the interface can be remarkably suppressed.

As described above, in the separator of the present invention, the adhesive porous layer has sufficient mechanical properties that can sufficiently withstand hot pressing and a uniform porous structure. Therefore, even when the amount of binder resin in the electrode is reduced and the hot press conditions are relaxed, superior adhesion is obtained compared to the conventional technology, and sufficient ion permeability is ensured even after bonding to the electrode. it can. Therefore, if such a separator is used, it is possible to provide a non-aqueous secondary battery having a high energy density and a high performance aluminum laminate pack exterior.

In order to obtain an adhesive porous layer as in the present invention, for example, a method of applying a polyvinylidene fluoride resin having a high weight average molecular weight can be mentioned, and specifically, a polyfluoride having 600,000 or more, preferably 1,000,000 or more is used. It is preferable to apply a vinylidene chloride resin. Another example is a method of increasing the content of vinylidene fluoride in the polyvinylidene fluoride resin. Specifically, it is preferable to use a polyvinylidene fluoride resin containing 98 mol% or more of vinylidene fluoride. Moreover, the method etc. which make the temperature of a coagulation bath lower and form a fine void | hole are also mentioned.

It should be noted that the adhesive porous layer can be mixed with fillers or other additives made of inorganic or organic substances within a range that does not impair the effects of the present invention. By mixing such a filler, it is possible to improve the slipperiness and heat resistance of the separator. As the inorganic filler, for example, a metal oxide such as alumina or a metal hydroxide such as magnesium hydroxide can be used. As the organic filler, for example, an acrylic resin or the like can be used.

[Separator for non-aqueous secondary battery]
As described above, the separator for a non-aqueous secondary battery of the present invention comprises a porous substrate and an adhesive porous layer containing a polyvinylidene fluoride resin formed on at least one surface of the porous substrate. I have. Here, since the adhesive porous layer is an adhesive layer that adheres to the electrode by hot pressing in a state containing the electrolytic solution, it needs to exist as the outermost layer of the separator. Of course, since it is preferable to adhere both the positive electrode and the negative electrode to the separator from the viewpoint of cycle life, it is preferable to form an adhesive porous layer on the front and back of the porous substrate.

In the present invention, the adhesive porous layer preferably has a sufficiently porous structure from the viewpoint of ion permeability. Specifically, the difference between the Gurley value of the porous substrate used and the Gurley value of the composite separator after forming the adhesive porous layer is 300 seconds / 100 cc or less, more preferably 150 seconds / 100 cc or less, More preferably, it is 100 seconds / 100 cc or less. When this difference is higher than 300 seconds / 100 cc, the adhesive porous layer is too dense to inhibit ion permeation, and sufficient battery characteristics may not be obtained.

The Gurley value of the separator for a non-aqueous secondary battery of the present invention is preferably in the range of 50 seconds / 100 cc to 800 seconds / 100 cc from the viewpoint of obtaining sufficient battery performance.

The porosity of the non-aqueous secondary battery separator is suitably in the range of 30% or more and 60% or less from the viewpoint of obtaining the effects of the present invention and good mechanical properties of the separator.

The weight of the polyvinylidene fluoride resin is preferably in the range of 0.5 g / m ² or more and 1.5 g / m ² or less on one surface from the viewpoint of adhesion to the electrode, ion permeability and battery load characteristics. It is. When the adhesive porous layers are formed on both the front and back surfaces, the total weight of the polyvinylidene fluoride-based resin is preferably 1.0 g / m ² or more and 3.0 g / m ² or less.

In the present invention, when the adhesive porous layer is formed on both surfaces of the porous substrate, the weight difference between the front and back surfaces is also important. Specifically, the total weight of both surfaces of the adhesive porous layer formed on the front and back of the porous substrate is 1.0 to 3.0 g / m ² , and the weight of one surface side of the adhesive porous layer is The weight difference on the other side is preferably 20% or less with respect to the total weight of both sides. If this exceeds 20%, curling may become prominent, which may hinder handling and may reduce cycle characteristics.

In the present invention, the curvature of the separator for a non-aqueous secondary battery is preferably in the range of 1.5 to 2.5 from the viewpoint of ensuring good ion permeability. The film thickness of the non-aqueous secondary battery separator is preferably 5 to 35 μm from the viewpoint of mechanical strength and energy density. The film thickness on one side of the adhesive porous layer is preferably in the range of 0.5 to 5 μm from the viewpoint of ensuring adhesion and good ion permeability. The fibril diameter of the polyvinylidene fluoride resin in the adhesive porous layer is preferably in the range of 10 to 1000 nm from the viewpoint of cycle characteristics.

The membrane resistance of the non-aqueous secondary battery separator is preferably in the range of 1 to 10 ohm · cm ² from the viewpoint of securing sufficient battery load characteristics. Here, the membrane resistance is a resistance value when the separator is impregnated with the electrolytic solution, and is measured by an alternating current method. Of course, although depending on the type and temperature of the electrolytic solution, the above numerical values are values measured at 20 ° C. using 1M LiBF ₄ propylene carbonate / ethylene carbonate (1/1 weight ratio) as the electrolytic solution.

[Method for producing separator for non-aqueous secondary battery]
The separator for a non-aqueous secondary battery of the present invention described above is an adhesive porous material in which a solution containing a polyvinylidene fluoride resin is directly applied onto a porous substrate to solidify the polyvinylidene fluoride resin. It can be manufactured by a method in which the layer is formed integrally on the porous substrate.

Specifically, first, a polyvinylidene fluoride resin is dissolved in a solvent to prepare a coating solution. This coating solution is applied onto the porous substrate and immersed in an appropriate coagulation solution. This solidifies the polyvinylidene fluoride resin while inducing a phase separation phenomenon. In this step, the layer made of polyvinylidene fluoride resin has a porous structure. Thereafter, the coagulating liquid is removed by washing with water, and the adhesive porous layer can be integrally formed on the porous substrate by drying.

As the coating liquid, a good solvent that dissolves the polyvinylidene fluoride resin can be used. As such a good solvent, for example, a polar amide solvent such as N-methylpyrrolidone, dimethylacetamide, dimethylformamide, dimethylformamide and the like can be suitably used. From the viewpoint of forming a good porous structure, it is preferable to mix a phase separation agent that induces phase separation in addition to the good solvent. Examples of such a phase separation agent include water, methanol, ethanol, propyl alcohol, butyl alcohol, butanediol, ethylene glycol, propylene glycol, and tripropylene glycol. Such a phase separation agent is preferably added in a range that can ensure a viscosity suitable for coating. Moreover, what is necessary is just to mix or melt | dissolve in the said coating liquid, when mixing a filler and another additive in an adhesive porous layer.

The composition of the coating solution preferably includes a polyvinylidene fluoride resin at a concentration of 3 to 10% by weight. As the solvent, it is preferable to use a mixed solvent containing 60% by weight or more of a good solvent and 40% by weight or less of a phase separation agent from the viewpoint of forming an appropriate porous structure.

As the coagulation liquid, water, a mixed solvent of water and the good solvent, or a mixed solvent of water, the good solvent, and the phase separation agent can be used. In particular, a mixed solvent of water, a good solvent, and a phase separation agent is preferable. In that case, the mixing ratio of the good solvent and the phase separation agent should be adjusted to the mixing ratio of the mixed solvent used for dissolving the polyvinylidene fluoride resin. From the viewpoint of The concentration of water is preferably 40 to 90% by weight from the viewpoint of forming a good porous structure and improving productivity.

The conventional coating methods such as Meyer bar, die coater, reverse roll coater, and gravure coater can be applied to the porous substrate. When the adhesive porous layer is formed on both sides of the porous substrate, it is possible to solidify, wash and dry after coating the coating solution one side at a time. From the viewpoint of productivity, it is preferable to solidify, wash and dry after coating.

In addition, the separator of this invention can be manufactured also with the dry-type coating method besides the wet coating method mentioned above. Here, the dry coating method is a method in which a coating liquid containing a polyvinylidene fluoride resin and a solvent is applied onto a porous substrate, and the solvent is removed by volatilization by drying the coating liquid. How to get. However, in the case of the dry coating method, the coating film tends to be a dense film compared to the wet coating method, and it is almost impossible to obtain a porous layer unless a filler or the like is added to the coating liquid. Moreover, even if such fillers are added, it is difficult to obtain a good porous structure. Therefore, from such a viewpoint, it is preferable to use a wet coating method in the present invention.

The separator of the present invention can also be produced by a method in which an adhesive porous layer and a porous substrate are prepared separately, and these sheets are superposed and combined by thermocompression bonding or an adhesive. As a method of obtaining the adhesive porous layer as an independent sheet, the coating liquid is applied onto the release sheet, and the adhesive porous layer is formed by using the wet coating method or the dry coating method described above. Examples include a method of peeling only the porous layer.

[Non-aqueous secondary battery]
The non-aqueous secondary battery of the present invention is characterized by using the separator of the present invention described above.
In the present invention, the non-aqueous secondary battery has a configuration in which a separator is disposed between a positive electrode and a negative electrode, and these battery elements are enclosed in an exterior together with an electrolytic solution. As the non-aqueous secondary battery, a lithium ion secondary battery is suitable.

As a positive electrode, the structure which formed the electrode layer which consists of a positive electrode active material, binder resin, and a conductive support agent on a positive electrode collector can be employ | adopted. Examples of the positive electrode active material include lithium cobaltate, lithium nickelate, spinel structure lithium manganate, and olivine structure lithium iron phosphate. In the present invention, when the adhesive porous layer of the separator is disposed on the positive electrode side, since the polyvinylidene fluoride resin has excellent oxidation resistance, LiMn _1/2 Ni _{1 1 that} can operate at a high voltage of 4.2 V or higher. There is also an advantage that a positive electrode active material such as ₂ O ₂ or LiCo _1/3 Mn _1/3 Ni _1/3 O ₂ can be easily applied. Examples of the binder resin include polyvinylidene fluoride resin. Examples of the conductive assistant include acetylene black, ketjen black, and graphite powder. Examples of the current collector include aluminum foil having a thickness of 5 to 20 μm.

As the negative electrode, a structure in which an electrode layer made of a negative electrode active material and a binder resin is formed on the negative electrode current collector can be adopted, and a conductive additive may be added to the electrode layer as necessary. As the negative electrode active material, for example, a carbon material that can occlude lithium electrochemically, a material that forms an alloy with lithium such as silicon or tin, and the like can be used. Examples of the binder resin include polyvinylidene fluoride resin and butylene-stadiene rubber. In the case of the separator for a non-aqueous secondary battery according to the present invention, since the adhesiveness is good, sufficient adhesiveness can be ensured even when not only polyvinylidene fluoride resin but also a butylene-stadiene rubber is used as the negative electrode binder. Examples of the conductive assistant include acetylene black, ketjen black, and graphite powder. Examples of the current collector include copper foil having a thickness of 5 to 20 μm. Moreover, it can replace with said negative electrode and can also use metal lithium foil as a negative electrode.

The electrolytic solution has a structure in which a lithium salt is dissolved in an appropriate solvent. Examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiClO _{4, and the} like. Examples of the solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, fluoroethylene carbonate, and difluoroethylene carbonate, chain carbonates such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and fluorine-substituted products thereof, γ-butyrolactone, γ -Cyclic esters such as valerolactone or a mixed solvent thereof can be suitably used. In particular, a solution in which 0.5 to 1.5 M of a lithium salt is dissolved in a solvent having a cyclic carbonate / chain carbonate = 20 to 40/80 to 60 weight ratio is preferable. In addition, in the separator provided with the conventional adhesive porous layer, it may be difficult to exhibit the adhesion to the electrode depending on the type of the electrolytic solution used, but according to the separator of the present invention, the type of the electrolytic solution However, there is a great advantage in that good adhesiveness can be exhibited.

The separator for a non-aqueous secondary battery of the present invention can be applied to a battery with a metal can exterior, but it is suitably used for a soft pack battery with an aluminum laminate film exterior because of its good adhesiveness to the electrode. In the method of manufacturing such a battery, the positive electrode and the negative electrode are joined via a separator, impregnated with an electrolytic solution, and enclosed in an aluminum laminate film. A non-aqueous secondary battery can be obtained by hot-pressing it. With such a configuration of the present invention, an electrode and a separator can be bonded well, and a non-aqueous secondary battery excellent in cycle life can be obtained. In addition, since the adhesion between the electrode and the separator is good, the battery is excellent in safety. There are a stack method in which the electrode and the separator are laminated, a method in which the electrode and the separator are wound together, and the present invention is applicable to any method.

Hereinafter, the present invention will be described by way of examples. However, the present invention is not limited to the following examples.

[Measuring method]
(Average pore size of adhesive porous layer)
By applying the BET equation by gas adsorption method to measure the specific surface area of the polyolefin microporous film and (m 2 ^{/ g),} a specific surface area of the composite separator forming the adhesive porous layer (m 2 ^{/ g).} The specific surface area (m ² / g) is multiplied by the basis weight (g / m ² ) to calculate the pore surface area per 1 m ^{2 of} the sheet. The pore surface area S per 1 m ² of the adhesive porous layer is calculated by subtracting the pore surface area of the polyolefin microporous membrane from the pore surface area of the composite separator. Separately, the void volume V per 1 m ^{2 of} sheet is calculated from the porosity. Assuming that all the holes are cylindrical, the average hole diameter (diameter) d is calculated from the hole surface area S and the hole volume V according to the following formula 2.

d = 4 × V / S (Formula 2)
d: average pore diameter of the adhesive porous layer V: pore volume of the adhesive porous layer S: pore surface area of the adhesive porous layer This d is the average pore diameter of the adhesive porous layer made of polyvinylidene fluoride resin It was.

(Film thickness)
It measured using the contact-type thickness meter (made by LITEMATIC Mitutoyo). The measurement terminal was a cylindrical one having a diameter of 5 mm, and was adjusted so that a load of 7 g was applied during the measurement.

(Weight)
A sample was cut into 10 cm × 10 cm and its weight was measured. The basis weight was determined by dividing the weight by the area.

(Weight of polyvinylidene fluoride resin)
The weight of the polyvinylidene fluoride resin was measured from the spectrum intensity of FKα using an energy dispersive X-ray fluorescence analyzer (EDX-800HS Shimadzu Corporation). In this measurement, the weight of the polyvinylidene fluoride resin on the surface irradiated with X-rays is measured. Therefore, when a porous layer made of polyvinylidene fluoride resin is formed on both the front and back surfaces, the weight of each polyvinylidene fluoride resin on the front and back surfaces is measured by measuring the front and back surfaces. The weight can be measured.

(Porosity)
The porosity ε (%) of the composite separator was calculated from Equation 3 below.

ε = {1− (Wa / 0.95 + Wb / 1.78) / t} × 100 (Formula 3)
Here, Wa is weight per unit area of the base material ^{(g /} m 2), Wb is weight of polyvinylidene fluoride resin (g ^{/ m} 2), t represents the thickness ([mu] m).

When calculating the porosity of the adhesive porous layer, in Equation 3 above, Wa = 0 (g / m ² ), and t is the thickness of the adhesive porous layer, that is, the thickness of the composite separator. This is obtained by subtracting the film thickness of

(Gurre value)
According to JIS P8117, it was measured with a Gurley type densometer (G-B2C manufactured by Toyo Seiki Co., Ltd.).

[Example 1]
KF polymer # 9300 (vinylidene fluoride / hexafluoropropylene = 98.9 / 1.1 mol% weight average molecular weight 1.95 million) manufactured by Kureha Chemical Co., Ltd. was used as the polyvinylidene fluoride resin. The polyvinylidene fluoride resin was dissolved in a mixed solvent having a dimethylacetamide / tripropylene glycol = 7/3 weight ratio at a concentration of 5% by weight to prepare a coating solution. This was coated on both sides of a polyethylene microporous membrane (TN0901: SK) having a film thickness of 9 μm, a Gurley value of 160 seconds / 100 cc, and a porosity of 43%, and water / dimethylacetamide / tripropylene glycol = 57 / It solidified by being immersed in the coagulation liquid (40 degreeC) of 30/13 weight ratio. This was washed with water and dried to obtain a separator for a non-aqueous secondary battery of the present invention in which an adhesive porous layer made of a polyvinylidene fluoride resin was formed on both front and back surfaces of a polyolefin microporous membrane. About this separator, the film thickness of the separator, the content of VDF in the polyvinylidene fluoride resin, the porosity of the separator (entire) and the adhesive porous layer (PVdF layer), the adhesive porous layer (PVdF layer) Table 1 shows the measurement results of average pore diameter and weight (total weight on both surfaces, surface weight, back surface weight, ratio of weight difference between the front surface side and back surface side to the total weight on both surfaces), and the Gurley value of the separator. The separators of the following examples and comparative examples are also collectively shown in Table 1.

[Examples 2 to 5]
Using the same coating liquid as in Example 1 and a polyethylene microporous membrane, the coating amount was changed as shown in Table 1 by the same method to obtain a separator for a non-aqueous secondary battery of the present invention.

[Examples 6 and 7]
Using the same coating liquid as in Example 1 and a polyethylene microporous membrane, by the same method, only the coating amount on the front and back sides was changed as shown in Table 1 to obtain the non-aqueous secondary battery separator of the present invention. It was.

[Example 8]
Except that a polyolefin microporous membrane (M824 Celgard) having a film thickness of 12 μm, a Gurley value of 425 seconds / 100 cc, and a porosity of 38% consisting of a three-layer structure of polypropylene / polyethylene / polypropylene was used as the polyolefin microporous membrane. The separator for non-aqueous secondary batteries of this invention was obtained like 1.

[Example 9]
A polyvinylidene fluoride resin having a copolymer composition of vinylidene fluoride / hexafluoropropylene / chlorotrifluoroethylene = 92.0 / 4.5 / 3.5 weight ratio was prepared by emulsion polymerization. The weight average molecular weight of this polyvinylidene fluoride resin was 410,000. A separator for a non-aqueous secondary battery of the present invention was obtained in the same manner as in Example 1 except that the polyvinylidene fluoride was used and the coating amount on both sides was 0.8 g / m ² .

[Comparative Example 1]
A polyvinylidene fluoride resin having a copolymer composition of vinylidene fluoride / hexafluoropropylene / chlorotrifluoroethylene = 92.0 / 4.5 / 3.5 weight ratio was prepared by emulsion polymerization. The weight average molecular weight of this polyvinylidene fluoride resin was 410,000. The polyvinylidene fluoride was dissolved in a mixed solvent having a dimethylacetamide / tripropylene glycol = 60/40 weight ratio at a concentration of 12% by weight to prepare a coating solution. This was coated on both sides of a polyethylene microporous membrane (TN0901: SK) having a film thickness of 9 μm, a Gurley value of 160 seconds / 100 cc and a porosity of 43%, and water / dimethylacetamide / tripropylene glycol = 50 / It solidified by being immersed in a 30/20 weight ratio coagulation liquid (40 degreeC). This was washed with water and dried to obtain a separator for a non-aqueous secondary battery in which a porous layer made of a polyvinylidene fluoride resin was formed on a polyolefin microporous film.

[Comparative Example 2]
The separator for the non-aqueous secondary battery was the same as Comparative Example 1 except that the concentration of the polyvinylidene fluoride resin was 8% by weight and the dimethylacetamide / tripropylene glycol was 55/45 weight ratio. Got.

[Comparative Example 3]
A non-aqueous secondary battery separator was obtained in the same manner as in Example 1 except that the temperature of the coagulation liquid was 0 ° C.

[Comparative Example 4]
KF polymer # 9300 (vinylidene fluoride / hexafluoropropylene = 98.9 / 1.1 mol% weight average molecular weight 1.95 million) manufactured by Kureha Chemical Co., Ltd. was used as the polyvinylidene fluoride resin. The polyvinylidene fluoride was dissolved in NMP at 5% by weight to prepare a coating solution. An equal amount of this was applied to both surfaces of a polyethylene microporous membrane (TN0901: SK) having a film thickness of 9 μm, a Gurley value of 160 seconds / 100 cc, and a porosity of 43%, and vacuum-dried at 100 ° C. for 12 hours. However, the obtained polyvinylidene fluoride film was dense and an adhesive porous layer could not be formed.

[Measurement of resistance of separator when impregnated with electrolyte]
The electrolyte solution was impregnated with 1 M LiBF ₄ propylene carbonate / ethylene carbonate = 1/1 weight ratio and impregnated with the electrolyte solution. This was sandwiched between aluminum foil electrodes with lead tabs and enclosed in an aluminum pack to produce a test cell. The resistance of this test cell was measured at 20 ° C. and −20 ° C. by the AC impedance method (measurement frequency: 100 kHz). This measurement was performed on Example 1, Comparative Examples 1 to 3 and the above-mentioned polyethylene microporous membrane (TN0901: manufactured by SK). The results are shown in Table 2. Moreover, the curvature was calculated by applying the following formula 4 from the obtained resistance value of 20 ° C. The results are also shown in Table 2.

τ = {(R · ε / 100) / (r · t)} ^1/2 (Formula 4)
τ: curvature R (ohm · cm ² ): resistance of separator when impregnated with electrolyte r (ohm · cm): specific resistance of electrolyte ε (%): porosity t (cm): membrane Thickness

[Interpretation of resistance measurement results]
The value obtained by dividing the resistance of −20 ° C. by the resistance of 20 ° C. is the same in Example 1, Comparative Example 2 and the microporous polyolefin membrane, while that of Comparative Example 1 is remarkably increased. . In the state in which the adhesive porous layer is impregnated with the electrolytic solution, the ions of the electrolytic solution present in the swollen resin have an extremely high moving speed compared to the ions of the electrolytic solution present in the pores. Late, the difference becomes more pronounced at lower temperatures. From this, compared with Example 1, the swelled resin contains a large amount of electrolyte and the amount of electrolyte present independently in the pores is smaller than that of Example 1. It is presumed that there was a difference in movement and the resistance value at low temperature was increased. In Comparative Examples 1 and 2, a polyvinylidene fluoride-based resin that is easily swelled in the electrolytic solution as compared with Example 1 is applied. When such a resin is applied, as the pore diameter is reduced, The amount of ions increases. Therefore, when such a resin is applied, if the pore diameter of the porous layer made of the polyvinylidene fluoride resin is reduced, ion permeability, particularly ion permeability at low temperature is lowered, which is not preferable. . On the other hand, in the case of Example 1, although the hole diameter is small, the resistance increase at a low temperature is small. This is because the polyvinylidene fluoride resin of Example 1 is relatively difficult to swell in the electrolyte solution. From this, it is preferable to select an appropriate polyvinylidene fluoride resin for the porous structure of the adhesive porous layer. I know it ’s good.

When comparing the curvatures of Example 1 and Comparative Examples 1 to 3, it can be seen that Example 1 is significantly smaller. Considering that the same polyolefin microporous membrane is used in all samples and that the thickness of the adhesive porous layer is significantly smaller than the thickness of the polyolefin microporous membrane, the curvature is the polyolefin microporous membrane. It is presumed to reflect the clogging of the interface between the adhesive and the adhesive porous layer. In other words, it can be said that the higher the curvature, the greater the degree of clogging. As described above, since the system of the comparative example uses a polyvinylidene fluoride resin that easily swells in the electrolyte, it is necessary to consider clogging due to this swelling. Based on the above-described contents, it is considered that the system having a large average pore diameter in Comparative Example 2 is less affected by swelling, but the curvature is significantly high even in such a system. This seems to reflect the fact that the adhesive porous layer in the present invention is fine and uniform porous and therefore is not prone to clogging stochastically. Accordingly, the porous structure as in the present invention can prevent clogging of the interface, and the configuration of the present invention is considered suitable from the viewpoint of ion migration.

In Comparative Example 3, the porosity of the porous layer made of the polyvinylidene fluoride resin is small, but in such a configuration, there are few pores formed in the porous layer made of the polyvinylidene fluoride resin. The formation of an interface with the polyolefin microporous film is not preferable, and clogging becomes remarkable, and therefore the curvature is high. Therefore, the membrane resistance is high at 20 ° C. or −20 ° C., and sufficient ion permeability is not obtained. This tendency is more remarkable at −20 ° C.

[Production of non-aqueous secondary battery]
(Preparation of negative electrode)
300 g of artificial graphite as negative electrode active material (MCMB25-28 manufactured by Osaka Gas Chemical Co., Ltd.) and “BM-400B” manufactured by Nippon Zeon as binder (water-soluble dispersion containing 40% by weight of modified styrene-butadiene copolymer) Liquid) 7.5 g, 3 g of carboxymethyl cellulose as a thickener, and an appropriate amount of water were stirred in a double-arm mixer to prepare a negative electrode slurry. This negative electrode slurry was applied to a 10 μm thick copper foil as a negative electrode current collector, and the obtained coating film was dried and pressed to prepare a negative electrode having a negative electrode active material layer.

(Preparation of positive electrode)
89.5 g of lithium cobaltate (cell seed C, Nippon Kagaku Kogyo Co., Ltd.) powder as a positive electrode active material, 4.5 g of acetylene black (Denka Black Denki Kagaku Kogyo Co., Ltd.) as a conductive auxiliary agent, polyvinylidene fluoride (KF) as a binder Polymer W # 1100 (manufactured by Kureha Chemical Co., Ltd.) was stirred in a double-arm mixer so that the weight of polyvinylidene fluoride was 6% by weight, and the positive electrode slurry was prepared. Produced. This positive electrode slurry was applied to a 20 μm thick aluminum foil as a positive electrode current collector, and the resulting coating film was dried and pressed to produce a positive electrode having a positive electrode active material layer.

(Production of battery)
A lead tab was welded to the positive electrode and the negative electrode, the positive and negative electrodes were joined via a separator, an electrolyte solution was impregnated, and sealed in an aluminum pack using a vacuum sealer. The electrolyte used here was 1M LiPF ₆ ethylene carbonate / ethyl methyl carbonate (3/7 weight ratio). A test battery was produced by applying a load of 20 kg per 1 cm ² of electrode with a hot press machine and performing hot pressing at 90 ° C. for 2 minutes.

[Load characteristic test]
The load characteristic test was performed using the produced non-aqueous secondary battery. The load characteristics of the battery were determined by measuring a relative discharge capacity of 2C with reference to a discharge capacity of 0.2C at 25 ° C., and using this as an index. This test was performed on batteries using the separators of Examples 1 to 9 and Comparative Examples 1 to 4. The results are shown in Table 3.

[Charge / discharge cycle test]
The charge / discharge cycle test was carried out using the produced non-aqueous secondary battery. The cycle characteristics test was performed under the condition that the charging conditions were constant current and constant voltage charging of 1C and 4.2V, and the discharging conditions were constant current discharging of 1C and 2.75V cutoff. Here, the index of the cycle characteristics was the capacity retention rate after 100 cycles. This test was performed on batteries using the separators of Examples 1 to 9 and Comparative Examples 1 to 4. The results are shown in Table 3.

[Check electrode and adhesion]
The battery after the charge / discharge cycle test was disassembled to confirm the adhesion between the separator and the electrode. The adhesiveness was confirmed from the viewpoint of adhesive strength and uniformity, and the results are shown in Table 3. In addition, regarding adhesive force, it shows in Table 3 by the relative value when the peeling strength at the time of using the separator of Example 1 is set to 100 about each of the positive electrode side and the negative electrode side. Regarding the uniformity, after performing a peel test on each of the positive electrode side and the negative electrode side, it was judged that the adhesive porous layer was almost entirely adhered to the electrode surface, and the uniformity was judged to be good (◯). Most of the porous layer is attached to the electrode surface, but the one that is partially damaged is judged to have a medium uniformity (△), and most of the adhesive porous layer is attached to the electrode surface. Those that were severely damaged were judged to have poor uniformity (x).

In Comparative Examples 1 and 2, the adhesiveness is not preferred, but this is because the average porous diameter of the adhesive porous layer is large and the porosity is high. This is because it could not endure, and was not held between the electrode and the separator and protruded outside. On the other hand, this was not the case in Examples 1-9. From this point of view, it can be seen that the average pore size and porosity of the non-aqueous secondary battery separator of the present invention are suitable.

[Heat resistance evaluation]
The heat resistance of the separator of Example 1 and that of Example 8 were compared by thermomechanical property measurement (TMA). Specifically, each separator was cut out to a width of 4 mm, and both ends thereof were pressed with a chuck, and set so that the distance between chucks was 10 mm. The applied load was 10 mN, the temperature was raised at a rate of temperature rise of 10 ° C./min, and the temperature at which the separator broke was measured. The separator of Example 1 was confirmed to break at 155 ° C., whereas the separator of Example 8 was confirmed to break at 180 ° C. It can be seen that applying polypropylene is preferable from the viewpoint of heat resistance.

[Electrolyte type and adhesion]
The separators of Example 1 and Comparative Examples 1 to 4 were tested for adhesion to electrodes using various electrolytes in the same manner as described above. In addition, 1M LiPF ₆ ethylene carbonate / ethyl methyl carbonate (3/7 weight ratio) is used as the electrolytic solution A, and 1M LiPF ₆ ethylene carbonate / propylene carbonate / ethyl methyl carbonate (3/2/5 weight ratio) is used as the electrolytic solution B. 1M LiPF ₆ ethylene carbonate / propylene carbonate (1/1 weight ratio) was used as the electrolytic solution C. The results are shown in Table 4. Table 4 shows the relative peel strength when the peel strength obtained for each of the positive electrode and negative electrode of the separator of Example 1 is 100, and the average peel strength between the positive electrode and the negative electrode is 70 or more. Is described as ◯, those of 50 or more and less than 70 are described as Δ, and those of less than 50 are described as ×.

The non-aqueous secondary battery separator of the present invention can be suitably used for a non-aqueous secondary battery, and is particularly suitable for a non-aqueous secondary battery having an aluminum laminate exterior, which is important for bonding with an electrode.

Claims

A separator for a non-aqueous secondary battery comprising a porous substrate and an adhesive porous layer containing a polyvinylidene fluoride-based resin formed on at least one surface of the porous substrate,
The adhesive porous layer has a porosity of 30% or more and 60% or less, and an average pore diameter of 1 nm or more and 100 nm or less.
The adhesive porous layer has a porosity of 30% to 50%,
The separator for a non-aqueous secondary battery according to claim 1, wherein the polyvinylidene fluoride resin contains 98 mol% or more of vinylidene fluoride.
The weight of the adhesive porous layer formed on one surface of the porous substrate is 0.5 g / m 2 or more and 1.5 g / m 2 or less. A separator for a non-aqueous secondary battery according to 1.
The separator for a non-aqueous secondary battery according to any one of claims 1 to 3, wherein the adhesive porous layer is formed on both front and back surfaces of the porous substrate.
The total weight of both surfaces of the adhesive porous layer formed on both surfaces of the porous substrate is 1.0 g / m 2 or more and 3.0 g / m 2 or less,
5. The non-aqueous secondary battery use according to claim 4, wherein the difference between the weight on one side of the adhesive porous layer and the weight on the other side is 20% or less with respect to the total weight of both sides. Separator.
The separator for a nonaqueous secondary battery according to any one of claims 1 to 5, wherein the porous substrate is a polyolefin microporous membrane containing polyethylene.
The separator for a non-aqueous secondary battery according to any one of claims 1 to 5, wherein the porous substrate is a polyolefin microporous film containing polyethylene and polypropylene.
The non-aqueous system according to claim 7, wherein the polyolefin microporous membrane has a structure of at least two layers, one of the two layers including polyethylene and the other layer including polypropylene. Secondary battery separator.
A non-aqueous secondary battery using the separator according to any one of claims 1 to 8.